en_tn_condensed/lev/13/55.md

after the item where there was leprosy was washed

"after they washed the item where there was leprosy"

leprosy

Here this probably refers to mildew. See how you translated this word in Leviticus 13:47.

it is unclean

Something that God has declared to be unfit for people to touch is spoken of as if it were physically unclean.

You must burn the item

Here "you" does not refer to the priest specifically. It just means someone must burn the object.